Toxicity analysis and public health aspects of municipal landfill leachate:

a case study of Okhla landfill, Delhi

Vijaya SinghA.K. Mittal

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ContentsW

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Introduction

– Scenario of landfilling in India– Leachate: why it is cause of concern?– Bioassay for toxicity analysis– Site details

Methodology and Experimental Set-up

– Leachate characterization and toxicity analysis– Fish bioassay set-up

Analysis of Results

Conclusions

IntroductionW

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Landfilling is the most common form of municipal solid waste (MSW) disposal in India

Daily MSW generation inDelhi is approx.7000 metric tons

Monthly leachate production estimated to be 81.5 m3

What is leachate and why it is cause of concern?

Leachate is defined as liquid that has percolated through solid waste and has extracted dissolved constituents of waste, soluble products of waste degradation process and suspended materials from it.

Studies have shown that leachate from MSW landfill canbe more toxic than hazardouswaste landfill leachate

Leachate seeping out of landfillis a threat to:– Ground water– Surface water

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Introduction

Bioassay toxicity testChemical analysis:

– Identifies the presence of specific compounds

– Not enough to assess the potential danger

Bioassay toxicity test:

– Can detect toxicity even when the contaminants are not identified

– Reflect the cumulative and synergistic effects of all the compounds

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Evaluation in short time (mortality is the end point)

Duration:

24 h – 96 h

Relates concentration to time of death for a particular test organism

Most frequently used (short = less expensive)

Evaluation takes longer since sub-lethal effects must be analyzed

Duration: 7-30 days (exposure for at least 1/10th of lifetime

Effect of concentration on growth, reproduction, behavioral, physiological or biological functions

Acute Chronic

Bioassay

Introduction

Delhi landfills

At present there are 3 landfill sites in Delhi – Okhla, Gazipurand Bhalsawa

Category: uncontrolled solid waste disposal facility

– No base liners– No gas or leachate collection

system

Leachate percolates down the ground surface, gets collected in low lying area, sometimes mixed up with sewer or drainage system

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Introduction

Adopted from Zafar and Alappat, (2004)

Okhla landfill site

Commissioned in 1996

Waste type: domestic waste (e.g. kitchen waste; paper, plastic, glass, cardboard and clothes), construction waste and unauthorized industrial waste

Waste density: 1200 kg/m3

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Okhla landfill site

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Leachate finds its way through an opening at the low lying area of the landfill

Leachate flowing freely on the ground

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Leachate sampling points

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Leachate from Okhla landfill flowing in the premises of adjacent residential area

Methodology: Leachate Characteristics

Leachate samples used in the fish bioassay were collected in the month of June and December 2007

Samples were always collected from 2 different places of the landfill site, namely;L1 & L2 collected in JuneL1 & L2 collected in December

The characteristics of leachate varied significantly with space and time 24,000 – 54,000TS

2,000 – 19,000TDS20,000 – 35,000TSS 1,000 – 3,000NH3-N 6,000 – 20,000COD 16,000 – 23,000Chloride 9,000 – 25,000Hardness12,000 – 32,000Alkalinity

7.6 – 8.2pH

Range of valuesa

Parameters

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aAll in mg/l except pH

Methodology: leachate toxicity

Acute toxicity (LC50) of leachate was determined using static 96 h fish bioassay

LC50: Lethal concentration that causes death for 50% of test organisms

Calculation method: Spearman-Karber method

Test organism: Poecilia reticulata (guppy fish)

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Set-up for toxicity testing

Range finding tests: conducted prior to 96h acute toxicity tests

X = Concentration of leachate in test solution (% v/v)

No. of test sp. In each container = 10 (mean wt. 0.2 – 0.4 g)

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Control X1% X2%

X3% X4% X5%

Results: Leachate toxicityW

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-20

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80

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7.5% 9.0% 12.0% 13.5% 15.0% 16.5%

Dilution of samples

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96-h LC50 = <13%

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20

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60

80

100

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10.0% 11.5% 13.0% 14.5% 15.5% 16.0%Dilution of samples

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y %

96-h LC50 = <12%

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40

60

80

100

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0.5% 1.5% 3.0% 4.5% 6.0% 7.5%

Dilution of samples

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96-h LC50 = <3%

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1.0% 2.0% 3.0% 4.0% 5.0% 6.0%Dilution of samples

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96-h LC50 = <4%

Toxicity assay L1 June 2007 Toxicity assay L2 June 2007

Toxicity assay L1 December 2007 Toxicity assay L2 December 2007

Results: Metals in the leachateMetals deemed as hazardous to environment and public health were detected

Non biodegradable and do accumulate in the food web

Pb – potential carcinogen, affects nervous system

Cd – carcinogen, affects hormone and enzyme system

Ni – carcinogen

Co, Cr, Zn and Cu – have been reported for various health problems

Fe and Ni – highest concentrarion in all the four leachate samples

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0.3 – 1.0Cobalt (Co)

1.0 – 5.0Nickel (Ni)

4.0 – 9.5Iron (Fe)

0.8 – 2.2Chromium (Cr)

0.8 – 1.5 Zinc (Zn)

0.2 - 0.5Manganese (Mn)

0.2 - 1.5Copper (Cu)

0.2 - 0.4Cadmium (Cd)

0.9 – 1.5Lead (Pb)

Range of valuesa

Metals

aAll values in mg/L

Organic compounds, toxicity and bioavailability

Landfill age >10 years: leachate may contain countless number of organic compounds

Organo-nitrogenated substances & heavy metals: – Highly toxic– High potential of bioavailability

Organo-halogenated compounds: can persist in aquatic environment and cause bioaccumulation

Factors affecting bioavailability:– pH– Ion exchange capacity– Water solubility

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The study shows a clear cut case of potential environmental pollution as indicated by the toxicity of Okhla leachate

No correlation was observed in the toxicological and physicochemical parameters of leachate

Presence of heavy metals in leachate supports the toxicity data

Ecotoxicological evaluation of leachate is fundamental for assessing the risk posed to environment and public health

Conclusions

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Thank you !!!